View of the beginning of Hoover Dam contruction at the bottom of Black Canyon. Various pieces of equipment, trucks, workers, etc. are visible including a crane suspended above the construction site. The view is from downstream.

This photo shows the construction of the foundation of Hoover Dam on the floor of Black Canyon. Trucks, construction equipment, and cranes can be seen as well as several construction buildings. Photo taken from high above the canyon.

View from on high of Hoover Dam construction, looking upstream. The Colorado River can be seen above the dam. Also shows concrete forms, a train winding along the side of the canyon, high scaling equipment, construction buildings, and a wire suspended above the canyon used to carry men and/or equipment across.

Overhead view of the construction of Hoover Dam in Black Canyon. Looking upstream, the Colorado River is visible above the dam site. Also shows concrete forms, a train winding along the side of the canyon, and various construction buildings.

Construction site of Hoover Dam in Black Canyon, looking upstream. Above the site is the Colorado River. Shows concrete forms, a train winding along the wall of the canyon, various construction buildings, hoisting machinery, and a cable suspended above the canyon for transporting men and materials.

View of Hoover Dam construction site, looking upstream. Above the site is the Colorado River. There are concrete forms, construction buildings, hoisting machinery, and a cable high above the Black Canyon in the picture. There is also a train winding along the wall of the canyon.

Construction photo of Hoover Dam in Black Canyon, showing the Colorado River above the dam site. Also shows concrete forms, a train winding along the canyon wall, high scaling and hoisting machinery, various construction buildings and a cable suspended above the canyon.

Overhead view of the construction of Hoover Dam in Black Canyon with the Colorado River visible above the dam site. In the photo are concrete forms, various construction buildings, a train winding along the side of the canyon, high scaling and hoisting machinery, and a cable suspended above the canyon.